Pippa Middleton on Cross-Country Charity Bike Ride

Pippa Middleton and her younger brother James are pedaling for charity in a cross-country trek from San Diego to Annapolis, Md., an epic ride called the "Race across America" in which the two will attempt to bike coast to coast through 12 states in eight days.

The team will try to cycle from 3 to 500 miles a day, some of which includes steep terrain. They reportedly plan to break up the race by tag-teaming so riders have a chance to rest, relax and eat while keeping pace with the schedule.

Kate Middleton's younger brother and sister are not new to ultra endurance events. They took part in a grueling Swedish seven-hour cross-country ski marathon in 2012, also to raise money for charity. And later this summer the two reportedly may also attempt the Bosphorus Cross Continental Swimming Race.

Pippa Middleton is expected to have loads of fans as she makes her away across the U.S. She has become a celebrity in the U.S., with her every move tracked since she stole the show in that stunning photo at her sister's wedding to Prince William.

Her poised demeanor and discretion have kept people intrigued and clamoring for any information about her life.

She and her brother are part of a team of eight bikers, including good friend James Matthews, who are raising money in honor of Matthews' brother who died while descending Mt. Everest in 1999.

She will also be raising money for the British Heart Foundation. She was recently made an ambassador and is hoping to raise awareness on heart disease and women's health.

"I was shocked to learn that nearly three times more women die from coronary heart disease than breast cancer," she said in a statement released by the BHF. "I'm passionate about raising awareness amongst women of this killer disease and I look forward to working with the BHF to highlight to women the risks of heart disease and importantly, how they can reduce them."

Both siblings have been busy. James Middleton has recently launched a very popular, very successful marshmallow confectionary company called Boomf. The novel idea allows patrons to customize their favorite photos or selfies on marshmallows, a kind of Willy Wonka 21st century style idea, mixing memories with sweet treats.

For now, though, the two just want to make it through this next challenge.